Polyphenylene sulphide-based compositions with improved impact strength and process for preparing them

ABSTRACT

Polyphenylene sulphide-based compositions essentially containing 60 to 99.5% by weight of polyphenylene sulphide and 0.5 to 40% by weight of a combination (C) containing a compound (C1) chosen from olefinic elastomers containing epoxy groups and a compound (C2) chosen from crosslinking agents containing functional groups which are reactive towards the epoxy groups of the compound (C1) and are chosen from amino, hydroxyl, carboxyl and carboxylic acid anhydride groups. They are obtained by melt-blending polyphenylene sulphide with each of the compounds (C1) and (C2) of the combination (C) successively and in any order.

This is a divisional of prior application Ser. No. 08/327,882, filedOct. 24, 1994, now U.S. Pat. No. 6,699,946 allowed, and a continuationof prior application Ser. No. 07/987,185, filed on Dec. 8, 1992, nowabandoned, the Disclosure of which is incorporated herein by reference.

The present invention relates to polyphenylene sulphide-basedcompositions with improved impact strength. It relates more precisely tocompositions containing a polyphenylene sulphide and a product resultingfrom the crosslinking of an olefinic elastomer containing epoxy groups.It also relates to a process for preparing these compositions.

Poly(phenylene sulphide) (referred to briefly as PPS hereinafter)exhibits an outstanding thermal stability and a very good chemicalresistance, which make it a material of choice for the moulding ofcomponents which can be employed especially in electrical and electronicapplications and in the motor vehicle industry.

However, PPS has the disadvantage of having a low impact strength andhence of being brittle.

Attempts have already been made to overcome this disadvantage byincorporating into PPS elastomeric copolymers derived from olefins andfrom glycidyl esters of alpha,beta-unsaturated carboxylic acids(Japanese Patent Application published under number 58-154757 (1983)(Toray Industries)). The insufficient reactivity of the molecular chainsof PPS towards the elastomeric copolymer nevertheless means that theinterfacial cohesion between the disperse elastomeric phase and thecontinuous phase containing the PPS is mediocre and that the improvementin the impact strength of PPS remains inadequate. Attempts havetherefore been made to increase the chemical affinity of PPS for theelastomeric copolymer by subjecting PPS beforehand to a treatment withacid and/or hot water (U.S. Pat. No. 4,889,893 (Toray Industries)).However, the morphology and the processability of the compositionsobtained is not satisfactory.

Patent Application FR-A-2,617,176 (Société Chimique des Charbonnages)describes compositions containing a material which may be a polyarylenesulphide and which is strengthened against impact by addition of acopolymer containing ethylene-derived units, units derived from at leastone aliphatic ester of an α,β-unsaturated carboxylic acid and unitsderived from maleic anhydride. The compositions may also contain achemical agent capable of crosslinking the copolymer and incorporated atthe time of the blending of the other constituents of the composition.The morphology of the compositions obtained is not satisfactory either.

It has also been proposed to improve the cohesion between the continuousphase containing the PPS and the disperse phase containing the elastomerby first melt-blending PPS with a polyfunctional isocyanate(4,4′-diphenylmethane diisocyanate) (Patent Application EP-A-0,406,553(Asahi Kasei)). The composition obtained contains thiourethane bondswhich impair its stability.

Patent Application EP-A-0,360,544 (Ube Industries) describedthermoplastic compositions comprising PPS and a vinyl copolymercontaining epoxy groups and which can also contain a styrene copolymermodified with carboxylic acid anhydride groups.

The mechanical and thermal properties and the processability of thesecompositions are, however, actually improved only when they additionallycontain a polyphenylene ether.

It has now been found that the impact strength of compositionscontaining PPS can be improved by incorporating therein a particularcrosslinked elastomer, using a particular method which makes it possibleto disperse it homogeneously in the PPS matrix without impairing thelatter's other properties.

Consequently, the present invention relates chiefly to polyphenylenesulphide-based compositions essentially containing 60 to 99.5% by weightof polyphenylene sulphide and 0.5 to 40% by weight of a combination (C)containing a compound (C1) chosen from olefinic elastomers containingepoxy groups and a compound (C2) chosen from crosslinking agentscontaining functional groups which are reactive towards the epoxy groupsof the compound (C1) and chosen from amino, hydroxyl, carboxyl andcarboxylic acid anhydride groups.

The polyphenylene sulphide (PPS) present in the compositions accordingto the invention is a polymer containing at least 70 mol %, preferablyat least 90 mol % of p-phenylene sulphide repeat units of formula

PPSs containing at least 70 mol % of p-phenylene sulphide repeat unitsimpart sufficient thermal stability and chemical resistance to thecompositions according to the invention. 30 mol % or less of the repeatunits present in the PPS may be chosen from those which have thefollowing structural formulae:

Processes for the manufacture of PPSs which can be employed according tothe invention are well known. They can all be employed. A processcomprises heating an alkali metal sulphide, in most cases sodiumsulphide hydrate, in a polar solvent in order to remove the water ofhydration therefrom, followed by the addition of a dihalogenatedaromatic compound, in particular p-dichlorobenzene, and polymerisationat higher temperature (see, for example, U.S. Pat. No. 3,354,129(Phillips Petroleum)). The molecular weight of the PPS obtained can beincreased in a known manner by oxidative aftertreatment resulting inbranched products or by addition of known agents for increasing themolecular weight (water, esters, anhydrides and alkali metalcarboxylates and sulphonates, etc.) to the polycondensation mixture,resulting in linear products of high molecular weight.

The molecular weight of the PPS which can be employed according to theinvention may vary within wide measures. It is generally such that themelt index of the PPS is between 5 g/10 min and 10,000 g/10 min,preferably between 10 g/10 min and 500 g/10 min (determined according toASTM standard D 1238-74 T at a temperature of 315° C. under a 5-kgload).

The PPS which can be employed according to the invention may containconventional additives in quantities which are not detrimental to theproperties of the compositions according to the invention. By way ofsuch additives there may be mentioned in particular: anti-oxidants andheat stabilisers such as, for example, hindered phenols, thioesters andphosphites, anti-UV agents such as, for example, resorcinol,benzotriazole and benzophenone, flame-retardant agents such as, forexample, antimony salts, aryl chlorophosphates and chlorinatedparaffins, antistatic agents such as, for example,dodecylbenzenesulphonate and polyalkylene glycols, lubricants such as,for example, graphite, molybdenum disulphide and silicones, corrosioninhibitors such as, for example, alkali metal carbonates, pigments suchas, for example, titanium dioxide and zinc sulphide, processing aidssuch as, for example, aromatic esters of phosphoric acid and microtalc,agents for controlling the degree of crosslinking such as, for example,peroxides, crosslinking accelerators such as, for example, metal saltsof thiophosphinic acid, crosslinking inhibitors such as, for example,dialkyltin dicarboxylates or aminotriazole, and the like.

Small quantities of other polymers may also be added to the PPS.

The PPS which can be employed according to the invention may also betreated to improve its affinity for the compound (C1) defined later,with an acid, hot water and/or an organic solvent. Details relating tothis treatment, which is known to a person skilled in the art, can befound in U.S. Pat No. 4,889,893 (Toray Industries).

The compositions according to the invention are obtained by introducinga combination (C) containing a compound (C1) and a compound (C2).

The compound (C1) which can be employed in the compositions according tothe invention is an olefinic elastomer containing epoxy groups. An“olefinic elastomer containing epoxy groups” is intended to denoteelastomeric copolymers derived from olefins and from monomers containingat least one epoxy group and at least one ethylenically unsaturatedradical (comonomer (1)).

The olefins from which these copolymers are derived may be α-monoolefinsor diolefins containing conjugated double bonds.

Specific examples of α-monoolefins are ethylene, propylene, 1-butene,isobutylene and the like. Ethylene is preferred as α-monoolefin.

Specific examples of diolefins containing conjugated double bonds are1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene,chloroprene, 1,3-pentadiene, 1,3-hexadiene and the like.

1,3-Butadiene is preferred as diolefin containing conjugated doublebonds.

The use of a number of different olefins to prepare the compound (C1)also comes within the scope of the invention.

The comonomers (1) from which the elastomeric copolymers (compound (C1))are derived may be chosen from glycidyl esters of α,β-unsaturatedcarboxylic acids corresponding to the general formula

in which R is a hydrogen atom or a C₁₋₈ alkyl radical.

Specific examples of glycidyl esters of α,β-unsaturated carboxylic acidsare glycidyl acrylate, glycidyl methacrylate, glycidyl α-ethylacrylate,glycidyl itaconate and the like.

The comonomers (1) may also be chosen from glycidyl ethers containing anethylenic unsaturation, such as allyl glycidyl ether, 2-methylallylglycidyl ether and styryl p-glycidyl ether, for example, or from othermonomers containing an epoxy group and an ethylenically unsaturatedradical, such as, for example, 3,4-epoxybutene,3,4-epoxy-3-methyl-1-butene, 3,4-epoxy-1-pentene,3,4-epoxy-3-methyl-1-pentene and 5,6-epoxy-1-hexene.

Glycidyl esters of α,β-unsaturated carboxylic acids are preferred ascomonomer (1) and, among these, most particularly glycidyl methacrylate.

Apart from the olefins and the comonomers (1), the compounds (C1) mayalso be derived from at least one other unsaturated comonomer (2) whichis copolymerisable with olefins. This comonomer (2) is generally chosenfrom:

-   -   alkyl esters of α,β-unsaturated carboxylic acids, such as, for        example, methyl acrylate and methacrylate, ethyl acrylate and        methacrylate, n-propyl acrylate and methacrylate, isopropyl        acrylate and methacrylate, n-butyl, isobutyl and t-butyl        acrylate and methacrylate,    -   vinyl esters of carboxylic acids, such as, for example, vinyl        acetate, vinyl propionate and vinyl benzoate,    -   styrene,    -   acrylonitrile, and the like.

Alkyl esters of α,β-unsaturated carboxylic acids are preferred ascomonomer (2), and among these, most particularly ethyl acrylate.

The compounds (C1) can be obtained in a known manner by copolymerisationof the corresponding monomers, for example by high-pressure radicalcopolymerisation of the corresponding monomers.

The quantity of olefin present in the compounds (C1) is generallybetween 50 and 90% by weight, preferably between 55 and 85% by weight ofthe compound (C1).

The quantity of comonomer (1) present in the compounds (C1) is generallybetween 0.1 and 40% by weight, preferably between 0.5 and 30% by weightof the compound (C1). When this latter compound also contains acomonomer (2), this comonomer represents between 0.5 and 50% by weight,preferably between 5 and 45% by weight of the compound (C1).

Quantities of monomer(s) (1) (and (2)) which are too small do not allowthe desired effects to be obtained, and quantities of monomer(s) (1)(and (2)) which are too high result in the formation of gels duringblending and a deterioration in the mouldability of the compositionsaccording to the invention.

Compounds (C1) which are particularly preferred contain from 60 to 80%by weight of ethylene as α-monoolefin, from 1 to 15% by weight ofglycidyl (meth)acrylate as comonomer (1) and from 15 to 40% by weight ofC₁₋₄ alkyl acrylate as comonomer (2).

The compound (C2) which can be employed in the compositions according tothe invention is a cross-linking agent containing functional groupswhich are reactive towards the epoxy groups of the compound (C1). A“crosslinking agent containing functional groups which are reactivetowards the epoxy groups” is intended to denote all the compoundscapable of inducing an at least partial crosslinking of the compound(C1), that is to say a bridging between the epoxy groups of themacromolecules of the compound (C1).

The compound (C2) is a nonpolymeric or polymeric polyfunctional compoundcontaining functional groups chosen from amino groups, hydroxyl groups,carboxyl groups and carboxylic acid anhydride groups.

Specific examples of nonpolymeric compounds (C2) containing amino groupsin their molecule are aliphatic polyamines such as ethylenediamine,1,6-hexamethylene-diamine, 1,3-diaminopropane, 1,4-diaminobutane,diethylenetriamine, triethylenetetramine, tetraethylene-pentamine,ethylaminoethylamine, 2-hydroxyethyl-aminopropylamine,iminobispropylamine and the like, alicyclic polyamines such asdiaminodicyclohexylamine, N-aminoethylpiperazine,1,3-diaminocyclohexane, bis(4-amino-3-methylcyclohexyl)methane and thelike, aliphatic polyamines containing an aromatic nucleus, such asm-xylylenediamine and the like, aromatic polyamines such asdiaminodiphenyl ether, diaminodiphenyl sulphone,4,4′-dimethylenedianiline, 4,4′-bis(o-toluidine),methylenebis(o-chloroaniline) and the like.

Specific example of polymeric compounds (C2) containing amino groups areethylene copolymers containing ethylenic units and units derived fromN,N-dialkyl-aminoalkyl esters of α,β-unsaturated carboxylic acids, suchas copolymers of ethylene and of N,N-dimethylamino-ethyl methacrylateand the like, copolymers of ethylene containing ethylenic units andunits derived from N,N-di-alkylaminoalkylamides of α,β-unsaturatedcarboxylic acids, such as copolymers of ethylene and ofN,N-di-methylaminopropylacrylamide, and the like.

Specific examples of nonpolymeric compounds (C2) containing hydroxylgroups are ethylene glycol, tetra-, hexa- and decamethylene glycols,trimethylolpropane, pentaerythritol and the like.

Specific examples of polymeric compounds (C2) containing hydroxyl groupsare phenol-formaldehyde resins of the resole and novolac types,hydrolysed ethylene-vinyl acetate copolymers and the like.

Specific examples of nonpolymeric compounds (C2) are dicarboxylic acidssuch as malonic acid, maleic acid, succinic acid, adipic acid, sebacicacid, phthalic acid and the like and tricarboxylic acids such astrimellitic acid and the like.

Specific examples of nonpolymeric compounds (C2) containing carboxylicacid anhydride groups are maleic anhydride, succinic anhydride, itaconicanhydride, dodecenylsuccinic anhydride, phthalic anhydride, tetra-hydro- and hexahydrophthalic anhydride, tetrabromophthalic anhydride,trimellitic anhydride and the like, maleic anhydride being preferred.

Specific examples of polymeric compounds (C2) containing carboxyl groupsor carboxylic acid anhydride groups are copolymers of olefins and of atleast one comonomer (3) chosen from unsaturated carboxylic acids and theanhydrides derived from these acids.

The olefins from which the above copolymers are derived correspond tothe same definitions and limitations as the olefins from which thecompounds (C1) are derived. Among olefins, α-monoolefins are preferredand, among the latter, ethylene is particularly suitable.

The comonomers (3) from which the above copolymers are derived arechosen from unsaturated carboxylic acids and the anhydrides derivedtherefrom. Specific examples of unsaturated carboxylic acids which canbe employed as comonomers (3) are acrylic acid, methacrylic acid, maleicacid, fumaric acid, itaconic acid, crotonic acid and the like. Specificexamples of anhydrides derived from these acids are maleic anhydride,itaconic anhydride and the like. Carboxylic acid anhydrides arepreferred as comonomer (3) and, among these, most particularly maleicanhydride.

Apart from the olefins and the comonomers (3), the compounds (C2) ofpolymeric type may also contain at least one other unsaturated comonomer(2′). This unsaturated comonomer (2′) corresponds to the samedefinitions and limitations as the comonomer (2) which can form part ofthe composition of the compounds (C1).

The quantity of olefin present in the copolymers of olefins and of atleast one comonomer (3) which are defined above and which can beemployed as compounds (C2), is generally between 50 and 98% by weight,preferably between 60 and 95% by weight of the copolymer.

The quantity of comonomer (3) present in these copolymers is generallybetween 0.1 and 30% by weight, preferably between 0.2 and 20% by weightof the copolymer. When these copolymers also contain an unsaturatedcomonomer (2′), this comonomer represents between 0.5 and 50% by weight,preferably between 2 and 35% by weight of the copolymer.

The olefin copolymers of the comonomer (3) and of the optional comonomer(2′) can be obtained in a known manner by high-pressure radicalcopolymerisation of the corresponding monomers.

Among all the compounds (C2) which can be employed in the compositionsaccording to the invention the preferred ones are the copolymers ofolefins, of the comonomer (3) and of the optional comonomer (2′).Specific examples of these copolymers are ethylene/maleic acidcopolymers, ethylene/maleic anhydride copolymers, ethylene/acrylic acidcopolymers, ethylene/methacrylic acid copolymers, ethylene/ethylacrylate/maleic acid copolymers, ethylene/ethyl acrylate/maleicanhydride copolymers, ethylene/ethyl acrylate/acrylic acid copolymers,ethylene/ethyl acrylate/methacrylic acid copolymers, ethylene/butylacrylate/maleic anhydride copolymers, ethylene/butyl acrylate/acrylicacid copolymers, ethylene/butyl acrylate/methacrylic acid copolymers,ethylene/vinyl acetate/maleic anhydride copolymers, ethylene/methylmethacrylate/maleic anhydride copolymers and the like.

The respective quantities of compounds (C1) and (C2) present in thecombination (C) are not critical, provided that the quantity of compound(C2) is sufficient to produce at least partial crosslinking of thecompound (C1). The quantities of compounds (C1) and (C2) are generallychosen so that the molar ratio (epoxy groups of the compound(C1))/(functional groups of the compound (C2) which are capable ofreacting with the epoxy groups of the compound (C1)) is between 0.1 and10.

Good results are obtained when this ratio is between 0.2 and 5.

At least some of the PPS-based compositions of the invention contain aparticular crosslinking product which the compositions belonging to theprior art do not contain. These compositions, which constitute aparticular subject-matter of the present invention, comprise 60 to 99.5%by weight, preferably 70 to 95% by weight, of a PPS matrix (continuousphase) and 0.5 to 40% by weight, preferably 5 to 30% by weight, of adisperse phase of a combination (C) containing the product of thecrosslinking of an elastomeric compound (C1) containing from 60 to 80%by weight of ethylene, from 1 to 15% by weight of glycidyl(meth)acrylate and from 15 to 40% by weight of C₁₋₄ alkyl acrylate bymeans of a compound (C2) containing from 65 to 95% by weight ofethylene, from 0.5 to 10% by weight of maleic anhydride and from 3 to30% by weight of C₁₋₄ alkyl acrylate, the compounds (C1) and (C2) havingbeen brought into contact in a molar ratio (epoxy groups of the compound(C1))/(anhydride functional groups of the compound (C2)) of between 0.8and 1.2.

Apart from the PPS and the combination (C), the compositions accordingto the invention may also contain other ingredients in quantities whichare not detrimental to the properties of these compositions. Thus, ingeneral, these compositions may contain from 5 to 300% of the weight ofPPS, preferably from 10 to 200% of the weight of PPS, of one or morefillers or of one or a number of reinforcing materials such as, forexample, glass fibres, talc, calcium carbonate, silica, alumina, mica,aluminium silicate, calcium silicate, magnesium oxide, metal powders,quartz powder, ballotini, carbon fibres, potassium titanate fibres,graphite, carbon black and the like; these fillers and these reinforcingmaterials may be surface-treated with coupling agents such as, forexample, silanes and titanates.

As mentioned above, the invention is aimed at improving the impactstrength of PPS-based compositions by incorporating the combination (C)therein by a particular method. This method, which is described below,ensures a homogeneous dispersion of fine particles of the crosslinkedcombination (C) in the PPS matrix of the said compositions. Anotheraspect of the invention therefore lies in the process for thepreparation of these compositions.

The process for the preparation of the compositions according to theinvention comprises the melt-blending of the mix containing the PPS (aswell as the optional “conventional additives” referred to above) and thecompounds (C1) and (C2) of the combination (C). According to theinvention this blending must be performed by incorporating each of thecompounds (C1) and (C2) of the combination (C), successively and in anyorder, into the PPS.

The blending may be performed in any device whatever which is capable ofbringing the PPS into the molten state and of subjecting it to intensivekneading in this state. In general, this kneading may be performedequally well in noncontinuous or continuous mixer of the external typeor of the internal type, such as those marketed by the companies Haake,Loedige, Troester, Wedco, Henschel, Banbury and others. For technicaland economic reasons it is preferred to work in mixers of the internaltype, in particular in extruders, which constitute a particular class ofinternal mixers. Although these extruders may be single-screw extruders,it is preferred to work in extruders with two mutually meshing screws(twin screws) rotating in the same direction (corotative twin screw).Well-known extruders of the above preferred type are, for example, thosemarketed by the company Werner & Pfleiderer under the name ZSK 30.

For the practical implementation of the process of preparation accordingto the invention in extruders, the latter are fitted with a secondaryfeed situated at a determined distance from the main feed along theextruder body. This distance can be determined by taking into accountthe teaching which follows, relating to the time (t) separating theincorporation of the compound (C1) (or (C2)) and the incorporation ofthe compound (C2) (or (C1)) into the PPS.

The kneading temperature is generally between 280 and 350° C.,preferably between 290 and 330° C. Temperatures which are too low do notpermit a sufficient melting of the PPS for a homogeneous dispersion ofthe combination (C) therein. Temperatures which are too high can resultin degradation of the PPS and/or of the compounds (C1) and/or (C2).

With regard to the quantity of combination (C) to be incorporated intothe PPS, and the respective quantities of compounds (C1) and (C2),reference will be made to the definitions and limitations mentionedabove in relation to the compositions themselves.

With regard to the way in which the compounds (C1) and (C2) areincorporated into the PPS, the operation can be carried out, forexample, according to one of the following methods of putting it intopractice:

-   (V) incorporation of the compound (C1) by dry mixing with the PPS,    melting and kneading of the molten mix (a) thus obtained,    incorporation of the compound (C2) into this mix (a) and kneading of    the molten mix (aa) thus obtained,-   (W) incorporation of the compound (C1) by dry mixing with the PPS,    melting and kneading of the molten mix (a) thus obtained,    incorporation of PPS mixed with the compound (C2) into this mix (a)    and kneading of the molten mix (aa)′ thus obtained,-   (X) incorporation of the compound (C2) by dry mixing with the PPS,    melting and kneading of the molten mix (b) thus obtained,    incorporation of the compound (C1) into this mix (b) and kneading of    the molten mix (bb) thus obtained,-   (Y) melting of the PPS and incorporation of the compound (C1) into    the molten PPS, kneading of the molten mix (c) thus obtained,    incorporation of the compound (C2) into this mix (c) and kneading of    the molten mix (cc) thus obtained,-   (Z) melting of the PPS and incorporation of the compound (C2) into    the molten PPS, kneading of the molten mix (d) thus obtained,    incorporation of the compound (C1) into this mix (d) and kneading of    the molten mix (dd) thus obtained.

Although each of the methods of implementation (V) to (X) results incompositions exhibiting advantageous properties, the methods ofimplementation (V) to (X) are preferred, most particularly the method ofimplementation (V), because it results in impact-resistant compositionsin which the combination (C) is dispersed most homogeneously in the PPSmatrix with good adherence to the latter.

The time (t) separating the incorporation of the compound (C1) (or (C2))and the incorporation of the compound (C2) (or C1)) into the PPS mayvary within a wide measure. It is a function especially of the capacityor of the throughput of the kneading device, of the kneading period, ofthe kneading temperature, of the respective quantities of PPS and ofcombination (C) in the mix and of the respective quantities of compounds(C1) and (C2) in the combination (C).

The optimum time (t) can be determined by taking into account theindications which follow.

The compound (C2) (or C1)) is added after a time (t) which is sufficientto allow the preliminary homogeneous dispersion of the compound (C1) (or(C2)) in the molten PPS matrix. A homogeneous dispersion is intended tomean a dispersion of the compound (C1) (or (C2)) in the form ofparticles of diameters which generally do not exceed 10 μm, preferablydo not exceed 5 μm, most particularly between 2 and 0.3 μm, which areuniformly distributed throughout the PPS matrix. The obtaining of thehomogeneous dispersion can be assessed, for example:

-   -   by examining by scanning electron microscopy a sample moulded        from the mix of PPS and of the compound (C1) (or (C2)), cooled        beforehand and treated with an appropriate solvent capable of        extracting the compound (C1) (or (C2)),    -   by measuring the torque of the kneading device (this operation        is easiest to carry out on a noncontinuous internal mixer) and        by incorporating the compound (C2) (or (C1)) into the mix of PPS        and of the compound (C1) (or (C2)) when this torque has reached        its minimum value.

A time (t) which is too short generally results in a prematurecrosslinking of the combination (C), producing a composition ofirregular morphology and consequently an inadequate impact strength. Atime (t) which is too long is not economical and can deteriorate thecompositions.

The above implies that the determination of the optimum time (t) maydemand some preliminary routine tests taking into account the factorswhich affect it.

By way of example, with the preferred mixing devices according to theinvention (corotative twin-screw extruders operating at approximately300° C. at a speed of rotation of between 100 and 300 revolutions perminute), the main feed (introduction of the PPS and of the compound (C1)(or (C2)) and the secondary feed (introduction of the compound (C2) (or(C1)) are arranged at a distance such that the time (t) taken by themolten mix to travel from the first to the second is between 10 secondsand 5 minutes, preferably between 15 seconds and 3 minutes.

The process according to the invention makes it possible to obtain agood dispersion of an elastomeric phase in a PPS matrix, with goodinterfacial cohesion. The compositions which result from the mixingaccording to the invention exhibit a greatly increased flexibility whencompared with PPS alone.

The compositions according to the invention can be converted by knownmoulding methods into injection-moulded articles and into extrudedarticles.

The applications are all those for which PPS is employed, namely theinjection moulding of technical components with, in this case, improvedimpact strength properties and better acoustic characteristics (noiseattenuation, which is important in the case of components such ascylinder head covers for motor vehicles), and the extrusion of pipes,filaments, films and the like.

The following examples illustrate the invention with reference to FIGS.1 to 4 which are attached to the description. Examples 1R and 4R aregiven by way of comparison.

FIG. 1 is a diagram illustrating the change, as a function of time(minutes) in the torque (kg m) of the noncontinuous Haake mixer used formelt-blending the compositions of Examples 1R (curve I), 2 (curve II)and 3 (curve III).

FIG. 2 reproduces a photomicrograph, obtained by scanning electronmicroscopy (SEM), of a fracture surface of a sample of the compositionof Example 1R.

FIG. 3 reproduces a photomicrograph, obtained by SEM, of a fracturesurface of a sample of the composition of Example 2.

FIG. 4 reproduces a photomicrograph, obtained by SEM, of a fracturesurface of a sample of the composition of Example 3.

EXAMPLE 1R

This example is given by way of comparison. 80 parts by weight of apartially crosslinked PPS powder marketed by Tohpren under the name T-4are mixed with 20 parts by weight of a combination (C) comprising 38parts by weight of a terpolymer (compound (C1)) containing

-   68% by weight of ethylene-   30% by weight of ethyl acrylate-   2% by weight of glycidyl methacrylate (Atochem product Lotader    AX8660)-   and-   62 parts by weight of a terpolymer (compound (C2)) containing-   91.8% by weight of ethylene-   4.9% by weight of butyl acrylate-   3.3% by weight of maleic anhydride.

The PPS and the compounds (C1) and (C2) are introduced simultaneouslyinto a noncontinuous Haake mixer adjusted to a temperature of 300° C.and rotating at a speed of 64 revolutions/minute. The kneading iscontinued for 6 minutes.

The change in the mixer torque as a function of time is shown by curve Iin the diagram of FIG. 1. No increase in the torque is noted during thekneading.

The morphology of the composition obtained is examined by SEM(magnification: 1540 times) on a sample whose surface has been treatedwith xylene and with ultrasonics. The photomicrograph obtained is shownin FIG. 2. This figure shows that the morphology of the compositionobtained is irregular (the network formed by the crosslinking has beentorn up by shearing in the mixer).

EXAMPLE 2

The procedure is as in Example 1R except that the compound (C2) isintroduced into the mixer 3 minutes after the introduction of the PPSand of the compound (C1).

The change in the mixer torque as a function of time is shown by curveII of the diagram of FIG. 1. An increase in the torque is noted as soonas the compound (C2) is introduced, an increase which is attributable tothe crosslinking of the combination (C).

The morphology of the composition obtained is examined by SEM(magnification: 1830 times) on a sample whose surface has been treatedwith xylene and with ultrasonics. The photomicrograph obtained is shownin FIG. 3. This figure shows that the morphology of the compositionobtained is very regular, the particles of the combination (C) which aredispersed in the PPS matrix exhibiting a mean diameter of approximately0.6 μm, being distributed homogeneously in the said matrix and adheringwell to the latter. The delayed incorporation of the compound (C2) hasresulted in a crosslinking (responsible for the increase in the mixertorque) which has stabilised the morphology of the composition.

EXAMPLE 3

The procedure is as in Example 1R except that the compound (C1) isintroduced into the mixer 3 minutes after the introduction of the PPSand of the compound (C2).

The change in the mixer torque as a function of time is shown by curveIII of the diagram of FIG. 1. An increase in the torque is noted as soonas the compound (C1) is introduced, an increase attributable to thecrosslinking of the combination (C).

The morphology of the composition obtained is examined by SEM(magnification: 1850 times) on a sample whose surface has been treatedwith xylene and with ultrasonics. The photomicrograph obtained is shownin FIG. 4. This figure shows that the morphology of the compositionobtained is very regular, the particles of the combination (C) dispersedin the PPS matrix exhibiting a mean diameter of approximately 1 μm,being distributed homogeneously in the said matrix and adhering well tothe latter. The delayed incorporation of the compound (C1) has resultedin a crosslinking (responsible for the increase in the mixer torque)which has stabilised the morphology of the composition.

EXAMPLE 4R AND EXAMPLES 5 TO 8

Example 4R is given by way of comparison.

In the case of these examples, a corotative twin-screw extruder marketedby Werner & Pfleiderer under the name ZSK 30 (L/d ratio=42), stabilisedat 300° C. and in which the speed of rotation of the screws is 300revolutions/minute, is employed.

The main feed (A1) and the secondary feed (A2) of the extruder areseparated by a distance corresponding to 10 d.

EXAMPLE 4R

The extruder is fed at A1 only, with PPS-T4 powder at a rate of 7kg/hour.

EXAMPLE 5

The extruder is fed:

-   -   at A1 at a rate of 6.7 kg/hour with PPS-T4 containing 7.5% by        weight of a ground terpolymer (compound (C2)) containing 68% by        weight of ethylene 24% by weight of ethyl acrylate 8% by weight        of maleic anhydride (Atochem product Lotader L3700),    -   and at A2 with the compound (C1) identified in Example 1R        (Atochem product Lotader AX 8660) (rate: 0.172 kg/hour).

EXAMPLE 6

The extruder is fed:

-   -   at A1, at a rate of 6.7 kg/hour, with PPS-T4 containing 15% by        weight of the product Lotader L3700,    -   and at A2 with the product Lotader AX 8660 (rate: 0.353        kg/hour).

EXAMPLE 7

The extruder is fed:

-   -   at A1, at a rate of 6.7 kg/hour, with PPS-T4 containing 2.5% by        weight of the product Lotader AX 8660,    -   and at A2 with the product Lotader L3700 (rate: 0.543 kg/hour).

EXAMPLE 8

The extruder is fed:

-   -   at A1, at a rate of 6.7 kg/hour, with PPS-T4 containing 5% by        weight of the product Lotader AX 8660,    -   and at A2 with the product Lotader L3700 (rate: 1.186 kg/hour).

EXAMPLE 9

The extruder is fed:

-   -   at A1 with PPS-T4 containing 22.1% by weight of the product        Lotader AX 8660, at a rate of 5.5 kg/h,    -   at A2 with PPS-T4 containing 3.5% by weight of maleic anhydride        (rate 0.5 kg/h).

Extrusion temperature: 300° C., at a speed of 250 revolutions/minute.

EXAMPLE 10

The extruder is fed:

-   -   at A1 with PPS-T4 containing 11.1% by weight of the product        Lotader AX 8660, at a rate of 5.5 kg/h,    -   at A2 with PPS-T4 containing 3.5% by weight of maleic anhydride        (rate 0.5 kg/h).

Extrusion temperature: 300° C., at a speed of 250 revolutions/minute.

The individual conditions and the results of these examples are collatedin the table below.

In this table: the Izod impact strength test is measured according tothe standard D 256-90b, the elongation at break: measured according toASTM standard D638 (conditions: 5 mm/s at 23° C., thickness of the testpieces: 4 mm).

The test pieces intended for these tests were obtained by injectionmoulding of samples of the compositions of Examples 4R to 8 on a Nestal60 press.

TABLE Molar ratio: Izod test epoxy groups/ (unnotched Elongation Mainfeed Secondary feed anhydride func- test piece) at break (A1) (A2)tional groups (J/m) (%) Example 4R PPS alone — — 115.8 1.2 Example 5PPS + 7.5% wt Product ±1 598 6.6 of product Lotader AX8660 Lotader L3700Example 6 PPS + 15% wt Product ±1 1398 13.1 of product Lotader AX8660Lotader L3700 Example 7 PPS + 2.5% wt Product ±1 746 12 of productLotader L3700 Lotader AX8660 Example 8 PPS + 5% wt Product ±1 1790 25 ofproduct Lotader L3700 Lotader AX8660 Example 9 PPS + 22.1% wt PPS + 3.5%wt 0.92 >1800 48 of product of maleic Lotader AX8660 anhydride Example10 PPS + 11.1% wt PPS + 3.5% wt 0.46 >900 40 of product of maleicLotader AX8660 anhydride

1. A process for preparing a polyphenylene sulphide compositionconsisting essentially of 60 to 99.5% by weight of polyphenylenesulphide and 0.5 to 40% by weight of a combination (C) containing acompound (C1) chosen from olefinic elastomers containing epoxy groupsand a compound (C2) chosen from crosslinking agents containingfunctional groups which are reactive towards the epoxy groups of thecompound (C1) and selected from the group consisting of amino, hydroxyl,carboxyl and carboxylic acid anhydride groups, wherein the processcomprises melt-blending a mix containing the polyphenylene sulphide andthe compounds (C1) and (C2) of the combination (C), wherein thisblending is performed by incorporating each of the compounds (C1) and(C2) of the combination (C), successively and in any order, into thepolyphenylene sulphide.
 2. The process of claim 1, wherein the processcomprises melt-blending the mix containing the polyphenylene sulfide andthe compounds C1 and C2 of the combination C in a corotative twin-screwextruder.
 3. The process of claim 1, wherein the compound (C1) isincorporated into the polyphenylene sulphide by dry mixing with thelatter, in that the molten mix (a) thus obtained is melted and kneadedand in that the compound (C2) is incorporated into this mix (a) and inthat the molten mix (aa) thus obtained is kneaded.
 4. The process ofclaim 1, wherein the compound (C2) is incorporated into a mix containingthe polyphenylene sulphide and the compound (C1) after homogeneousdispersion of the compound (C1) in the molten polyphenylene sulphidematrix.
 5. The process of claim 1, wherein the compound (C1) isincorporated into a mix containing the polyphenylene sulphide and thecompound (C2) after homogeneous dispersion of the compound (C2) in themolten polyphenylene sulphide matrix.
 6. The process of claim 1, whereinthe compound (C2) is incorporated into a mix containing thepolyphenylene sulphide and the compound (C1) after melting of a mix (a)resulting from the homogeneous dispersion of the compound (C1) in themolten polyphenylene sulphide matrix and granulation of this mix (a). 7.The process of claim 1, wherein the compound (C1) is incorporated into amix containing the polyphenylene sulphide and the compound (C2) aftermelting of a mix (a) resulting from the homogeneous dispersion of thecompound (C2) in the molten polyphenylene sulphide matrix andgranulation of this mix (a).
 8. The process of claim 1, in which thecompound (C1) is incorporated into the polyphenylene sulphide by drymixing with the latter, melting is carried out and the molten mix (a)thus obtained is kneaded, the compound (C2) mixed with the polyphenylenesulfide is incorporated into this mix (a), and the molten mix (aa)′ thusobtained is kneaded.
 9. The process of claim 1 wherein the polyphenylenesuphide composition consists of 60 to 99.5% by weight of polyphenylenesulphide and 0.5 to 40% by weight of a crosslinked combination (C)consisting essentially of: a compound (C1) consisting of an elastomericcopolymer derived from at least one olefin and at least one comonomer(1) containing at lest one epoxy group and at least one ethylenicallyunsaturated radical, and at least one other unsaturated comonomer (2),an alkyl ester, of an α,β-unsaturated carboxylic acid, and a polymericcrosslinking agent (C2), consisting of a copolymer of an olefin and ofat least one comonomer (3) selected from the group consisting ofunsaturated carboxylic acids and carboxylic acid anhydride groupsderived from these acids, and at least one other unsaturated comonomer(2′) selected from alkyl esters of an α,β-unsaturated carboxylic acid,said crosslinking agent (C2) being crosslinked with said compound (C1).10. The process according to claim 9, wherein the comonomer (1) is aglycidyl ester of α,β-unsaturated carboxylic acid.
 11. The processaccording to claim 9, in which the crosslinking agent (C2) is acopolymer of an olefin and of maleic anhydride, and at least one otherunsaturated comonomer (2′) selected from alkyl esters of anα,β-unsaturated carboxylic acid.
 12. The process according to claim 9,wherein the quantities of compounds (C1) and (C2) which are present inthe combination (C) are chosen so that the molar ratio (epoxy groups ofthe compound (C1))/(functional groups of the compound (C2) which arecapable of reacting with the epoxy groups of the compound (C1)) isbetween 0.1 and
 10. 13. The process according to claim 1, wherein thecombination (C) consists essentially of the product of the crosslinkingof an elastomeric compound (C1) containing from 60 to 80% by weight ofethylene, from 1 to 15% by weight of glycidyl (meth) acrylate and from15 to 40% by weight of C₁₋₄ alkyl acrylate by means of a compound (C2)containing from 65 to 95% by weight of ethylene, from 0.5 to 10% byweight of maleic anhydride and from 3 to 30% by weight of C₁₋₄ alkylacrylate, the compounds (C1) and (C2) having been brought into contactin the molar ratio (epoxy groups of the compound (C1))/(anhydridefunctional groups of the compound (C2)) of between 0.8 and 1.2.
 14. Theprocess of claim 1 wherein the polyphenylene sulphide compositionconsists of 60 to 99.5% by weight of polyphenylene sulphide and 0.5 to40% by weight of a crosslinked combination (C) consisting of: a compound(C1) consisting of an elastomeric copolymer derived from at least oneolefin and at least one comonomer (1) containing at least one epoxygroup and at least one ethylenically unsaturated radical, and at leastone other unsaturated comonomer (2), an alkyl ester, of α-β-unsaturatedcarboxylic acid, and a polymeric crosslinking agent (C2), consisting ofa copolymer of an olefin and of at least one comonomer (3) selected fromthe group consisting of unsaturated carboxylic acids and carboxylic acidanhydride groups derived from these acids, and at least one otherunsaturated comonomer (2′) selected from alkyl esters of anα-β-unsaturated carboxylic acid, said crosslinking agent (C2) beingcrosslinked with said compound (C1).